Sensor-equipped wheel bearing device

Abstract

A sensor-equipped wheel support bearing assembly is provided which performs high-accuracy load estimation without providing with another sensor, even in a state where a ground contact load on a wheel supported by the bearing is very low as compared to other wheels. The assembly includes: a plurality of sensor units ( 20 ) detecting a load on a wheel support bearing segment ( 100 ); sensor signal calculator ( 31 ) processing sensor signals (S) from the units; and load calculation processor ( 32 ) calculating a load on a road surface contact point on a wheel, based on the processed information. The processor ( 32 ) determines whether a target wheel is in a predetermined low load state, based on information of a detected load on a wheel other than the target wheel; and switches a load calculation scheme in accordance with a result of the determination to calculate a load on the wheel.

What is claimed is: 
     
         1 . A sensor-equipped wheel support bearing assembly comprising:
 a wheel support bearing segment for rotatably supporting a vehicle wheel relative to a vehicle body structure, the bearing segment including: an outer member having an inner periphery formed with a plurality of rows of raceway surfaces; an inner member having an outer periphery formed with raceway surfaces that faces the respective raceway surfaces in the outer member; and a plurality of rows of rolling elements interposed between the facing raceway surfaces of the respective outer and inner members;   a plurality of sensor units provided in the wheel support bearing segment, each sensor unit being configured to detect a load applied to the wheel support bearing segment;   a sensor signal calculator configured to process output signals from the plurality of sensor units to generate an input signal vector; and   a load calculation processor configured to calculate a load applied to a road surface contact point on the wheel supported by the wheel support bearing segment, on the basis of the input signal vector generated by the sensor signal calculator, wherein   the load calculation processor includes: a low load state determination section configured to determine whether a target wheel which is the wheel supported by the wheel support bearing segment is in a predetermined low load state, based on information of a calculated load acting on at least one or more wheels which is provided in the same vehicle as the target wheel, but other than the target wheel; and a load estimation calculation section configured to switch a load calculation scheme in accordance with a result of the determination by the low load state determination section to calculate the load applied to the road surface contact point on the wheel, based on the input signal vector.   
     
     
         2 . The sensor-equipped wheel support bearing assembly as claimed in  claim 1 , wherein the determination as to the predetermined low load state by the low load state determination section is performed on the basis of a determination as to whether a ground contact load Fz applied to the target wheel is within a predetermined low load state region. 
     
     
         3 . The sensor-equipped wheel support bearing assembly as claimed in  claim 1 , wherein the low load state determination section is provided in a load sensor ECU including an electric control unit. 
     
     
         4 . The sensor-equipped wheel support bearing assembly as claimed in  claim 1 , wherein the low load state determination section is provided in a host ECU including an electric control unit serving as a host with respect to a load sensor ECU including an electric control unit and configured to transmit the result of the determination to the load sensor ECU. 
     
     
         5 . The sensor-equipped wheel support bearing assembly as claimed in  claim 1 , wherein the switching of the load calculation scheme in accordance with the result of the determination in the load estimation calculation section includes switching of a load estimation coefficient. 
     
     
         6 . The sensor-equipped wheel support bearing assembly as claimed in  claim 1 , wherein the switching of the load calculation scheme in accordance with the result of the determination in the load estimation calculation section includes switching of a configuration of the input signal vector to be used by the load calculation process. 
     
     
         7 . The sensor-equipped wheel support bearing assembly as claimed in  claim 1 , wherein the low load state determination section determines whether the target wheel is in the predetermined low load state, by using information of detected loads on a wheel at a laterally opposite side of the vehicle with respect to the target wheel, a wheel at a diagonally opposite position with respect to the target wheel, or both the wheel at the laterally opposite side and the wheel at the diagonally opposite position. 
     
     
         8 . The sensor-equipped wheel support bearing assembly as claimed in  claim 7 , wherein the low load state determination section uses, as an evaluation value for performing the determination, a ground contact load Fz applied to the wheel support bearing segment, an axial load Fy applied to the wheel support bearing segment, or a value which is a combination of the ground contact load Fz and the axial load Fy. 
     
     
         9 . The sensor-equipped wheel support bearing assembly as claimed in  claim 7 , wherein when, on an Fy-Fz plane with Fy and Fz indicating an axial load and a ground contact load, respectively, two points on the plane for the axial loads Fy and the ground contact loads Fz applied to two diagonal wheels deviate from point-symmetrical positions by a given amount with respect to an origin, at which the axial load Fy is equal to a load at a steering neutral position and the ground contact load Fz is equal to a wheel load, the low load state determination section determines that a wheel having a ground contact load Fz lower than the wheel load is in the low load state. 
     
     
         10 . The sensor-equipped wheel support bearing assembly as claimed in  claim 1 , wherein the low load state determination section switches a threshold serving as a reference for the determination between at ON of a brake and at OFF of the brake based on brake information of the vehicle, and performs the determination as to the predetermined low load state. 
     
     
         11 . The sensor-equipped wheel support bearing assembly as claimed in  claim 1 , wherein the low load state determination section includes a compensation processing section for considering different wheels of the vehicle as being under an equal condition. 
     
     
         12 . The sensor-equipped wheel support bearing assembly as claimed in  claim 11 , wherein the compensation processing section compensates a difference in mounting angle of a wheel of the vehicle. 
     
     
         13 . The sensor-equipped wheel support bearing assembly as claimed in  claim 11 , wherein the compensation processing section compensates a difference in geometry of a suspension at wheels of the vehicle. 
     
     
         14 . A sensor-equipped wheel support bearing system comprising:
 a plurality of wheel support bearing segments;   a plurality of sensor units provided in each of at least two wheel support bearing segments of the plurality of wheel support bearing segments, each sensor unit being configured to detect a load applied to the corresponding wheel support bearing segment;   at least one sensor signal calculator; and   at least one load calculation processor, wherein   each of the plurality of wheel support bearing segments for rotatably supporting a vehicle wheel relative to a vehicle body structure includes: an outer member having an inner periphery formed with a plurality of rows of raceway surfaces; an inner member having an outer periphery formed with raceway surfaces that faces the respective raceway surfaces in the outer member; and a plurality of rows of rolling elements interposed between the facing raceway surfaces of the respective outer and the inner members,   the at least one sensor signal calculator processes output signals from the plurality of sensor units provided in the at least two wheel support bearing segments, to generate input signal vectors, and   the at least one load calculation processor calculates loads applied to road surface contact points on the wheels supported by the respective at least two wheel support bearing segments, based on the input signal vectors, and includes: a low load state determination section configured to, for the target wheel on which the load is calculated, determine whether the target wheel is in a predetermined low load state, based on information of a calculated load acting on a wheel other than the target wheel; and a load estimation calculation section configured to switch a load calculation scheme in accordance with a result of the determination by the low load state determination section to calculate the load applied to the road surface contact point on the wheel, based on the input signal vector.   
     
     
         15 . The sensor-equipped wheel support bearing system as claimed in  claim 14 , wherein the determination as to the predetermined low load state by the low load state determination section is performed on the basis of a determination as to whether a ground contact load Fz applied to the target wheel is within a predetermined low load state region.